Conventionally, zoom lenses for various cameras are formed, for example, of three-group construction and include, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group. Zoom lenses with this construction have been widely used in order to produce a compact zoom lens with good correction of aberrations. For digital cameras and video cameras that have been widely used in recent years, as with zoom lenses for camera use in general, a small lens that enables high picture quality and low distortion is desired. Additionally, it is necessary to satisfy particular conditions due to the use of a solid state image pickup element, such as a CCD.
Recently, in these digital cameras and video cameras where a solid state image pickup element, such as a CCD, is used, the demand for a wider angle of view in the lens has become extremely strong. For example, there is a demand for a zoom lens in a thirty-five millimeter format camera to have a wide-angle focal length of approximately twenty-eight millimeters to twenty-four millimeters.
In a camera where a solid state image pickup device is used, it is possible to process an imaged picture into different pictures. This image processing, including image enlargement and cropping of an image taken at a wider angle, enables producing an image that simulates an image taken at the telephoto end to some extent. However, it is difficult to simulate a picture taken at a wide-angle from an image taken at the telephoto end. Therefore, it is necessary to optically obtain pictures at the wide-angle end.
Japanese Laid-Open Patent Application 2003-035868, Japanese Laid-Open Patent Publication 2001-296476, and Japanese said-Open Patent Publication 2000-284177 disclose zoom lenses designed for satisfying the requirements discussed above. The zoom lenses described in Japanese Laid-Open Patent Application 2003-035868 are mountable on a digital camera or a video camera where a solid state image pickup device, such as a CCD, is used. These zoom lenses have a three-group construction, wherein it is possible to zoom in and out within the range of focal lengths of twenty-six to eighty millimeters in terms of a thirty-five millimeter format camera. However, in the zoom lenses described in Japanese Laid-Open Patent Application 2003-035868, the first lens group from the object side, which is a lens group moved during zooming, is formed of three lens components that are lens elements so that it is difficult to satisfy the demands of compactness, which are currently strong for digital cameras and video cameras.
It has been accepted to use a minimum of three lens components that are lens elements for the first lens group in order to obtain acceptable optical performance at the wide-angle end of the zoom range of such zoom lenses. It has been considered difficult to make the first lens group more compact, for example, by including only two lens elements in the first lens group, with the optical performance being unsatisfactory, including unsatisfactory spherical aberration, distortion, lateral color, and image surface curvature (also known as field curvature).